Charge separation in nanoscale photovoltaic materials: recent insights from first-principles electronic structure theory

In this feature article we focus on the key problem of charge separation in nano-scale photovoltaic materials; in particular recent theoretical/computational work based on first principles electronic structure approaches is presented and discussed. We review applications of state-of-the-art electronic structure calculations to nano-scale materials that enable charge separation between an excited electron and hole in so-called excitonic photovoltaic cells. Emphasis is placed on theoretical results that provide insight into experimentally observed processes, which are yet to be understood and do not appear to obey a single unique model but rather depend on atomistic details. Examples are provided that illustrate how computational approaches can be employed to probe new directions in materials design for inducing efficient charge separation. We also discuss the computational challenges in electronic structure theory for reliably predicting and designing new materials suitable for charge separation in photovoltaic applications.